Re: [Xen-devel] [PATCH RFC] xen/evtchn: Implement EVTCHNOP_send_imm as a companian to EVTCHNOP_send

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 14 Jul 2017, Jan Beulich wrote:
> >>> On 13.07.17 at 09:50, <andrew.cooper3@xxxxxxxxxx> wrote:
> > --- a/xen/common/event_channel.c
> > +++ b/xen/common/event_channel.c
> > @@ -1098,6 +1098,10 @@ long do_event_channel_op(int cmd, 
> > XEN_GUEST_HANDLE_PARAM(void) arg)
> >          break;
> >      }
> >  
> > +    case EVTCHNOP_send_imm:
> > +        rc = evtchn_send(current->domain, (unsigned long)arg.p);
> 
> Two more things: For one this discards the upper half of the 64-bit
> handle. I'd suggest you instead check it to be zero.

+1, keeping in mind that arg will be 32-bit on ARM32 platforms and
64-bit on ARM64 platforms.

Moreover, evtchn_send takes an unsigned int as argument, why are you
casting arg.p to (unsigned long)?


> And then x86's do_event_channel_op_compat() should refuse to handle
> "immediate" commands.

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